I know the windings need to be phased. I've never done this but I
gather all that needs to be done is to measure the voltage out. It
should be the same when two are connected in paralell. If less, then
one is out of phase. I don't know any other way to tell if my home
wound windings are connected correctly. I do know that there are phase
dots on some xmfrs that I have on the shelf.

Almost correct, BUT!!

Place the two windings in series, If the voltage across the two free windings
is zero, then you can connect them together and the windings will be
paralleled. Connecting them in parallel wrong will give you maximum fault
current.

If you read twice the voltage of either one seperatly, then they are phased
wrong. Reversing the primary phase is usually easier than trying to rewire the
secondary.

Unless the two transformers are identical, you will probably have some small
voltage difference in the two windings. That will cause some loss due to
circulating currents, probably not too important unless its more than 1/2 volt
or so. Connecting transformer secondaries in parallel is not common due to this
problem. But, for an intermittant service where the primaries are switched, I
wouldn't worry about that.

Earle Rich
Mont Vernon, NH